div{
    $north_height: 100px;//顶部高度
    $south_height: 20px;//底部高度
    $west_width: 20px;//左边宽度
    $east_width: 20px;//右边宽度
    &.g-north,&.g-west,&.g-center,&.g-south,&.g-east{
        position:absolute;
        left:0;
    }
    &.g-north,&.g-south{
        width:100%;
    }
    &.g-west,&.g-east,&.g-center{
        top:$north_height;
        bottom:$south_height;
        _height:100%;
        overflow:auto;
    }
    &.g-north{
        top:0;
        height:$north_height;
    }
    &.g-west{
        width:$west_width;
    }
    &.g-east{
        right:0;
        width:$east_width;
    }
    &.g-center{
        _position:relative;
        left:$west_width;
        right:$east_width;
        _top:0;
        _left:0;
        _margin-left:$west_width;
    }
    &.g-south{
        bottom:0;
        height:$south_height;
    }
}